1. Field of the Invention
The present invention relates generally to semiconductor laser devices and, more particularly, is directed to a semiconductor laser device in which a semiconductor laser chip is mounted on a part of a semiconductor substrate on which an APC (automatic power control) photodiode is formed.
2. Description of the Prior Art
In the prior art, as a semiconductor laser device, there is a semiconductor laser device as shown in FIG. 1 in which an APC (automatic power control) photo diode b is formed on a surface portion of a semiconductor substrate (e.g., N.sup.+ type) a and a semiconductor laser chip c is mounted on a portion of the semiconductor substrate a near the portion where the APC photodiode b is formed. Then, as a manufacturing method for producing such semiconductor laser device, the method as generally shown in FIG. 2 has been proposed by applicant. This previously proposed manufacturing method will be described briefly. At first, as shown in FIG. 2A, by carrying out a series of treatments for a semiconductor wafer containing a plurality of substrates a, a, a, an APC photodiode b is formed on a part of each of the element-forming regions d d . . . . In FIG. 2A, reference letters f designate lines which partition the adjacent element-forming regions d, d, . . . and along which the element-forming regions d, d, . . . are to be diced. Then, as shown in FIG. 2B, the surface of the semiconductor wafer is half-diced along the lines f, f, . . . to thereby form grooves g, g, . . . . Thereafter, as shown in FIG. 2C, a semiconductor laser chip c is positioned on the solder layer e of each of the element-forming regions d, d, . . . . While in this state, the semiconductor wafer is passed through a heating furnace (for example at a heating temperature of 250.degree. C.) to thereby carry out the chip bonding of the respective semiconductor laser chips c, c, . . . simultaneously to their respective substrates a, a. Then, after the electrical characteristic and the optical characteristic are measured and inspected, and the necessary screening carried out, the semiconductor wafer is separated along the grooves g, g, . . . to thereby carry out pellet separation. Thereafter, as shown in FIG. 2E, The pellet a is pellet-bonded to a heat sink i which is located on a surface of a stem not shown. Thus, leads j and j attached to the stem are wire-bonded to the laser chip c and the electrode of the APC photodiode b respectively by wires K, the semiconductor laser device being thus practically mounted.
In this prior art manufacturing method for producing the semiconductor laser device, since the semiconductor laser chip is not bonded to the semiconductor substrate of an individual pellet but is bonded to the semiconductor substrate of a wafer at element-forming regions, there is the advantage that the semiconductor laser chips can be bonded simultaneously on a vast number of element-forming regions formed on one semiconductor wafer. In addition, when the semiconductor substrate is still in the wafer state, an electrical characteristic such as a threshold current Ith and the like can be measured by using a probe, and the screening carried out. Accordingly, not only the cost necessary for the bonding of the semiconductor laser device can be decreased but also the costs necessary for the test and the screening can be decreased. Accordingly, the above mentioned method is very advantageous.
However, in the prior art, when the semiconductor substrate a is still in the wafer state, it is impossible to measure and test the intensity of the laser emission from the semiconductor laser chip c and the symmetrical property of a far field pattern thereof. If upon cracking of the semiconductor laser chip or the like, the laser emission cannot be generated or the laser emission cannot reach a prescribed reference value. Similarly, an asymmetrical property of the far field pattern may be caused relatively easily by the positional displacement of the semiconductor laser chip c in its direction relative to the semiconductor substrate (a). If such positional displacement is beyond the tolerance range, the semiconductor laser device must be regarded as a bad or inferior product. Such bad product must be removed at an early stage as possible, otherwise, the inferior semiconductor laser devices are subjected to the pellet bonding to the heat sink i and the wire bonding are useless steps are carried out. This uselessness causes the manufacturing cost of the semiconductor laser device to be increased and fights a desired decrease in the manufacturing cost of the semiconductor laser device.